Is blindsight in normals akin to blindsight following brain damage?

Emotional priming depends on the degree of conscious experience

Most experiments in consciousness research assume that awareness is a dichotomous 'either/or' phenomenon. However, participants can distinguish multiple levels of subjective experience of simple features (colour, shape etc.), which correlate with their performance in different tasks. As experiments showing multiple levels of perceptual awareness question the widespread idea that many forms of perception can occur unconsciously, we investigated emotional priming combined with methods able to measure small variations in subjective experience.

We show awareness of emotional faces is gradual rather than dichotomous, and that the effects of emotional priming are predicted by the level of perceptual awareness of emotional faces, with no effects when reported unseen.

The results question how much unconscious perceptions can influence behaviour. As priming is one of the most well-established phenomena believed to occur unconsciously, the results expand the growing body of evidence that questions the contributions of unconscious processing on behaviour.

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Emotional priming is considered fundamental evidence for unconscious perception.

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Emotional priming strength is predicted by graded perceptual awareness levels.

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Emotional priming with faces is not effective when faces are reported as unseen.

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Facial expression recognition increases gradually with perceptual awareness levels.

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Perceptual awareness of faces increases gradually with duration of face stimuli.

Blind-Sight vs. Degraded-Sight: Different Measures Tell a Different Story

Blindsight patients can detect, localize, and discriminate visual stimuli in their blind field, despite denying being able to see the stimuli. However, the literature documents the cases of blindsight patients who demonstrated a preserved degree of awareness in their impaired visual field. The aim of this study is to investigate the nature of visual processing within the impaired visual field and to ask whether it reflects pure unconscious behavior or conscious, yet degraded, vision. A hemianopic patient (SL) with a complete lesion to the left primary visual cortex was tested. SL was asked to discriminate several stimulus features (orientation, color, contrast, and motion) presented in her impaired visual field in a two-alternative forced-choice task. SL had to report her subjective experience: in the first experiment as “seen” or “guessed,” whereas in the second experiment as the degree of clarity of her experience according to the perceptual awareness scale. In the first experiment, SL demonstrated a performance above-chance in the discrimination task for “guessed” trials, thus showing type 1 blindsight. In the second experiment, however, SL showed above-chance performance only when she reported a certain degree of awareness, thus showing that SL’s preserved discrimination ability relies on conscious vision. These data show that graded measures to assess awareness, which can better tap on the complexity of conscious experience, need to be used in order to differentiate genuine forms of blindsight from degraded conscious vision.

Chapter 13: the contributions of neurophysiology to clinical neurology an exercise in contemporary history

This chapter reviews a number of historical contributions of neurophysiology to clinical neurology in the hundred years that have elapsed since the publication of Sherrington's The Integrative Action of the Nervous System, a book generally considered the neurophysiologist's bible. In the past, many normal nervous functions have been inferred from disorderly functions in animals by neurophysiologists and in humans by clinical neurologists. If neurophysiologists have undoubtedly learned much from experimental lesions in animals, it has been the clinical neurologists who have obtained first-hand information on the effects of pathology on the functioning of the most complex and interesting of all nervous systems, that of man. Currently this division of labor is less clear, and convergent evidence from neurophysiology and clinical neurology alike has set our current knowledge about brain functions on a firm comparative foundation. This review of the relations between neurophysiology and clinical neurology reports contributions that have been recognized as "historical" by the scientific community because of their documented impact on the development of the entire field of neurosciences. The inclusion of further less famous neurophysiological achievements is justified by their potential influence on the advancement of neuroscience, as seen from the author's personal viewpoint.

Pediatric neuro-ophthalmology

PURPOSE OF REVIEW

This review will update the ophthalmologist on recent developments in pediatric neuro-ophthalmology.

RECENT FINDINGS

Research into the genetics of congenital strabismus syndromes has brought new insights into the development of the ocular motor system. There is also new literature on childhood ocular myasthenia gravis and childhood neurosarcoidosis. The results of three different surgical treatments for congenital nystagmus are described. Reviews on cortical visual impairment, dyslexia, Aicardi syndrome, and neuronal ceroid lipofuscinosis are presented.

SUMMARY

Pediatric neuro-ophthalmology is a diverse and challenging field. As we strive to provide excellent care to these patients, we will use the results of basic science, genetic, and neurobiological research.